By default, optimization messages have Remark severity. Specifying --diag_suppress=optimizations suppresses optimization messages.

The compiler performs certain high-level vector and scalar optimizations when compiling at the optimization level -O3 -Otime, for example, loop unrolling. Use this option to suppress diagnostic messages relating to these high-level optimizations.

int factorial(int n)
{
    int result=1;
    while (n > 0)
        result *= n--;
    return result;
}

Compiling this code with the options -O3 -Otime --remarks --diag_suppress=optimizations suppresses optimization messages.